Group III-V nitride semiconductors have been variously applied to optical devices such as blue and green light emitting diodes (LEDs), high speed switching devices such as a Metal Semiconductor Field Effect Transistor (MOSFET) and a Hetero junction Field Effect Transistor (HEMT), and light sources of lighting devices or display devices. Especially, a light emitting device using a group III nitride semiconductor has a direct transition-type band gap corresponding to the ranges from a visible ray to an ultraviolet ray to realize high efficient light emission.
The nitride semiconductor is mostly applied to LEDs or laser diodes (LDs). Research for improving a manufacturing process or light efficiency has been continuously made.